The invention relates to a method for extracting a protein from milk, having at least one hydrophobic pocket and a negative charge to the natural pH of milk, that comprises the following steps: a) skimming and delipidation of the milk; b) passing the delipidated and skimmed fraction containing the protein on a chromatographic substrate on which is grafted a ligand having both a hydrophobic characteristic and an ionic characteristic in pH conditions enabling the protein to be retained on the substrate, the pH being higher than 4.6; c) elution of the protein; d) purification of the eluted fraction by removing the milk proteins from the eluted fraction; and e) recovering the protein.